Processes are known for the production of polybutadienes wherein a high percentage of the 1,3-butadiene units are present in the cis-1,4-configuration. The majority of these processes are of the continuous type and involve the polymerization of 1,3-butadiene in an inert liquid polymerization medium in the presence of a homogeneous catalyst system prepared by the combination of a transition metal salt, in particular, a cobalt salt, with an R.sub.n AlX.sub.3-n aluminum compound such as an alkyl aluminum dihalide or a dialkyl aluminum monohalide or mixtures thereof. However, there is a tendency for gel to be formed in addition to the high cis-1,4-polybutadiene. The gel can take the form of small suspended particles which have an adverse effect on the quality of the high cis-1,4-polybutadiene produced or the gel can be of the type that adheres to the walls of the vessels containing the polymerization mixture and to the heat transfer surfaces thereby affecting the heat transfer of the equipment necessary for proper control of the reaction. Thus the formation of gel in either form is, desirably, to be avoided.
Furthermore, with increasing environmental concerns over the use of aromatic and halogenated hydrocarbon solvents in large scale manufacturing processes, it would be advantageous if a catalyst system that does not require the use of such solvents could be developed for use in the polymerization of 1,3-butadiene to high cis-1,4-polybutadiene.